1. Field of the Invention
This invention is related to optical inspection instrumentation and, in particular, to an apparatus and method that can be utilized in comprehensive eye diagnosis.
2. Discussion of Related Art
Visual field testing is a conventional clinical method utilized in the diagnosis of eye diseases that cause degradation of vision sensitivity. One of the most accepted methods utilized in the diagnosis of such diseases is the Standard Automated Perimeter (SAP) test, which tests brightness contrast sensitivity over a large visual field. There are many instruments for performing an SAP test routinely used in clinics including, for example, those produced by Carl Zeiss Meditec (Dublin, Calif.).
Typically, visual field testing utilizes functional field testing techniques. However, a functional field test technique is a functional test of vision degradation. Due to the human eye's complex multiplexing capability, the functional field test is not a sensitive measure of eye structure, which would be highly useful in the early diagnoses of such eye diseases before substantial degradation has occurred. Such structural tests include, for example, retinal image testing and optical coherence tomography.
Retinal image testing can be performed with conventional optical imaging methodology and has been routinely used in clinics for retinal structure change evaluation in addition to visual field tests. Devices such as a fundus camera or an indirect ophthalmoscope are routinely used for such testing. The retinal image provides valuable information that clinicians can utilize to diagnosis eye diseases. However, only qualitative interpretation of eye structure changes from the retinal photographs can be observed by highly experienced clinicians.
Optical Coherence Tomography (OCT) is a new imaging modality that has been used for non-invasive human eye retinal imaging. The cross sectional retinal image allows a clinician to quantitatively evaluate the retinal nerve layer and retinal thickness. Valuable clinical information can be extracted for early diagnosis of eye diseases, such as Glaucoma. However, at the end stage of the disease, when the patient s lose most of their Retinal Nerve Fiber Layer (RNFL), the OCT imaging method has certain technical difficulties in accurately measuring the RNFL. Therefore, it is difficult to follow the progression of diseases, such as glaucoma, with OCT techniques.
In light of the above-mentioned disadvantages over individual examination methods, clinicians need to have multiple examination results in comprehensive eye examinations to accurately assess the condition of the eye and detect diseases before patients exhibit overt symptoms. Currently, these exams are done separately on different instruments. At most, two methods are combined, as in, for example, the Microperimeter produced by Nidek Corp, Japan. Currently, there is no apparatus that is able to integrate a visual field test and OCT together. Therefore, there is a need for instruments for eye examination that allow a clinical practitioner to fully evaluate the structure of the eye in order to help diagnose and treat eye disease.